Arrangement in directed radio beacons



June 23,1959

Filed Nov. 8, 1955 F. J'. FRANSSON ARRANGEMENT IN DIRECTED'RADIO BEACONS v 2 Sheets-Sheet 1 Lung/av ATTORNEY June 1959 F. J. FRANSSON ,89 90 ARRANGEMENT IN DIRECTED RADIO BEACONS Filed Nov. 8, 1955 I 2 Sheets-Sheet 2 5 ,c: a; j 19 46 V g6 19 .50 I I I 45 INVENTOR ATTORNEYS niteci 2,892,190 Patented June 23, 1959 ARRANGEMENT. INDIRECTED RADIO BEACONS Frans Joel Fransson, Lidingo, Sweden, assignor to Svenska Aktiebolaget Gasaccumul'ator, Lidingo, Sweden, a corporation of Sweden Application November 8, 1955, Serial No. 545,665

Claims priority, applicationiswedcnDecember.6, 1954 7 Claims. (Cl. 343-107) Directed radio beacons have been more and more used as approaching beacons. radio beacons. is included the so-called course indicating beacons, which functionin such away that'one listening to the signal from'thec'ourse indicating radio beacon by' means of an open antenna and a usual radio receiver which, disregarding "the wave-length, may be a normal broadcast receiver. This radio beacon, has the purpose of indicating a given course'with a high degree of precision, said course being'followed when approaching a harbour through a narrow channel past an amount of subwater rocks or the like, and the beacon is made in suchaway that when deviating from thefstat'ed course in one direction, one'will hear a signal characteristic for this direction, and when deviating in the other direction, one will-hear another signal. These signals are preferably composed: by two Morse signs, complementing eaclrother asfor instance the Morse letters a-and n or e'anclt. When one is in the indicated course, one. will thus hear both of the Morse signs with the same in tensity, and as these are complementing each other, they are not'heard separately but together in a continuous tone.

Previously a radio transmitter was" combined with two antenna systems, one ot-wh-ich had adirection characten isticlike the figure 8, whereas the other one had a circular direction characteristic. The composed direction characteristic then acquired a form which should-"theoretically be exactly a cardioidic curve, if'the twodirection characteristics had the same maximum. signallintensity. Asza-matter of fiactthe 'characteristic deviates a-little from this-exactlfornn lln modern system'sof thiskind the idea of provding-Jcne'antenna: system :asan: open antenna a circular .characteristic-has-becn abandoned, and in mayacasethekdirected antenna system has not beenprovided as aframe antenna, i.e. in: such a formthat the: most pointed. out direction diagram sim ilaigwto;the figurezii will be obtained, the obtained (111766.- ti on. characteristic is indicated ascardioi'dic even though this is a little misleading;v In the'following the indication of cardioidic direction characteristic will: be .used in the last-mentioned, broaden meaning, 7 g

y changing,- the phase direction of the voltage with which one of the antenna systems is..fed,..one will then note that the. cardioidic direction characteristic swings toand fro, around an unsymmetrical axis, whichcauses the. signal" intensity in agiven direction alternatively to. be stronger and weaker. The change in, phase direction takes place in time with. the given complementary code, Only in the direction, marking. the level for the swinging axis ofthe direction" characteristic, one will obtain a constant signal intensity; and'this level is then used as course indicating level; by the antenna system being mountedin such a direction; that'this level coincides withthe-coursewhieh'shouid beindicated.

A; very commonformof sucheourse indicating, di rected radio beaconsiisausing: two usual frame antennas, placed in .thesameaplace in mntuallyperpendiculandh rections.

One frame antenna will then transmit its field in: the marked course directiomwhereas the other frame antenna transmits its field ina level perpendicular there to: The invention will for thesake of simplicitybe described below in connection with a system, containing such antenna systems, but it is understood that the invention is not therefor limited to the use only in connection with such antenna systems, and also that the obtained characteristic, although below mentioned as a cardioidic characteristic, may rather considerably deviate from the-mathematical cardioidiccurve.

Among such directed Common to all kinds of such directed radio beacons as mentioned above is that the course indication maybe made very sharp, but also that the demand for sharpness inthe course indication is only gained at the cost of a decrease of the signal intensity of the antenna systems and consequently also of the range of the beacon. However, cases may occur when it is of a very great importance to obtain both high direction sharpness and great range. This is for instance the case when the. beacon is used as. an approaching beacon of a harbour, which is placedat thebottom of a deep bay or other" navigatable channel, within which one requires a high sharpness of direction, but otherwise is facing open water, so that it is of importance that one should already at a great distance'from the radio beacon get contact with.

it". "In such cases, however, there is considerably less demandfor a high sharpness.

"The present invention relates to an arrangement in directed radio beacons of the common kind now men-' tioned ,.by which the demand for high sharpness of course, indication close at hand is met and there is also provided. great range with a decreased sharpness. I

The invention will be described below in connection 'a chosen form of execution, shown on the attached drawings, in which Fig. 1 gives an example of topographical-circumstances where a directed radio beacon of the present kind may be of value, Fig. 2 and Fig. 3 indicating two different examples of direction diagrams. Fig.4 shows a principal wiring diagram of a radio bea con'according to the'invention, and-Fig. 5 shows a diagram of elements of the wiring system.

ln Fig. 1 it is assumed that'the beacon is placedas an approaching beaconofthecity' Town, which is situated at the bottom of the deep and narrow Bay which eiittends inwards from the open water Sea. I-tis further assumed that the 'Bay' has substantially an eastward di rectionand that the subwater rock" in this Bay is of such aiki nd thatit is necessary to keep a very exactly determined" course when approaching the city Town. The coastaon each side of the mouth of the Bay is, however, such; that'the. sailing onto the coast-may take place from. any deliberate direction within an angle which passes from northcourse pas-t westerly course to southerlycourse. It is thus desirable that outside the mouth of Bay the same directed radio beacon shall be used asan approaching beacon towards the coast line, but there,-

obviously, the sharpness of, course indication must be essentially less. This has been indicated in Fig. 1 by means of the angles B and'y, limited by dash-dot. lines, the angle 13 indicating thesha'rpness of course indication i when sailing in Bay, whereas the angle indicatesthe lit-whereas the other frame antenna 1 1- is directed inf such a way that its direction diagram with i-ts long'it'udinal" symmetry axis falls perpendicularly to thecourse" line 12. The first mentioned diagram is indicated 13 and the latter one 14. It is now assumed that both of the frame antennas are fed from the same generator, and that they are mutually alike, so that the two direction characteristics are symmetrical, although displaced by 90 in the horizontal plane. In this case the precision of the arrangement will be very low. The sharpness of course indication may be indicated as the angle between the direction of the course and the direction, indicating equally strong field intensities from both direction diagrams. If this angle of sharpness is indicated n then it will obviously be 45 in the example, shown in Fig. 2, or in other words tan 04 :1. As a matter of fact, for the angle (1 the tangent of the angle is equal to the field intensity of the direction of the course, divided by the field intensity across said course direction.

For a deliberate angle on therefore the field intensity in the direction on is equal to F =f cos a+f sin a, when the current in one antenna system is in counterphase to the current of the other antenna system, and

when the current in both of the antenna systems is in phase. In these equations f indicates the field intensity in the direction 12 from the antenna 11 and f indicates the field intensity across the direction 12 from the antenna 10. The course width, or in other words the angle 18 or 7, within which the two signs may practically be understood by the human car as equally strong, and where one thus can no longer apprehend any difierence in sound intensity and consequently also not separate the signs from each other, is dependent upon the magnitude of the angle a From practical experience one knows of counse that the relation between the width of the course and the angle (t is different for difierent listeners, but it is assumed that this relation may with good approximation for practical needs be put to which would in other words mean that in the case, shown in Fig. 2, the width of the course should be 4.5. It is assumed that this course width is too big for approaching in the Bay.

It is now possible to decrease the value of the course width or, in other words, of the angle d by decreasing the field intensity f,, in the direction of the course, as evident from Fig. 3. The direction diagram 14 from the frame antenna 10 is there the same as in Fig. 2, but the field intensity in the course direction has been decreased, so that the direction diagram 13 is replaced by a much weaker direction diagram 13. It is also evident that the angle ca has been decreased to the value 0: The course angle has of course thereby decreased proportionally, but it is regrettable that also the signal intensity in the course direction has decreased proportionally to the decreased field intensity. Thereby the range of the beacon has been limited in such a way, that it may be assumed that it may only be well heard up to the distance circle 15, see Fig. 1, whereas it had been desirable to be able to hear the indication up to the distance circle 16. Within the field between the two distance circles 15 and 16, however, the course angle need not at all be small, and it may even be of advantage to the navigator that the course angle be wider. It is true that one could increase the range of the radio beacon in such a way that it may be well heard up to the distance circle 16, but this would mean that the system would be more expensive and it would mean an increase of the risk for reflections of the radiation to be of such an intensity to be heard separately. It must be kept in mind that for the radio beacons now in question substantially short and ultra-short wave-lengths are used, and these are especially adapted for forming of reflections. Further the advantage of the wider course angle at greater distances from the coast line would be lost.

Here the invention sets in: The feeder conduit to the antenna, which is active in the course direction, i.e. the antenna 11, may be switched in such a way that one alternatively feeds a higher amount of power and a smaller amount of power to this antenna, and during each of the periods for higher or smaller power, respectively, a signal is transmitted during repeated reversals of phase of one antenna, for instance also the antenna 11.

An arrangement for execution of this function is schematically shown in Fig. 4. An oscillator or transmitter is there indicated by 17. This oscillator or transmitter is by means of the conduits 18 connected to the antenna 10. A branch conduit 19 leads to the phase reverser 20, which is schematically indicated in the form of a twopole switch. This would not need any further description, because it is known per se to the man, skilled in the art, in many difierent forms. The output conduits 21 from the phase reverser 20 lead to the second antenna 11. The phase reverser 20 is suitably controlled by electromagnetic means from a pulse transmitter 22. This is schematically indicated by means of the conduits 23 from the pulse transmitter to a relay winding 24, the armature 25 of which is assumed to control the contacts of the phase reverser 20.

In the parts hitherto described the arrangement according to Fig. 4 is known. The new items according to this invention constitute a filter device connected into the conduit 18 and/or 19 with the function that when the filter is connected into this conduit, the signal intensity from the antenna 11 is heavily reduced, and when the filter is disconnected, the same signal intensity is again increased to its initial value. It is assumed that the filter contains the inductance coil 2627, one part 26 of which is continuously connected in the conduit 19 to the antenna 11, whereas the other part 27 can periodically be bypassed or connected into the conduit by means of a contact 28, subordinated under a relay 29, said relay being by means of the conduits 30 connected to the code transmitter 22. It is without any decisive importance to this invention, how the tuning of the transmitter 17 takes place, but for the sake of simplicity it is assumed that this tuning takes place by means including a condenser 31. It is now obvious that the circuit will be disaligned, when the inductance 27 is connected into it. For resetting the alignment to its correct value a further condenser 32 is therefore provided to be connected in parallel to the condenser 31 by means of a contact 33, which is also controlled by the relay 29.

It is assumed that in the radio beacon now shown the transmitter is audio frequency modulated. The moduletor is in a way known per se built into the transmitter 17. As this is well known to every man skilled in this art, no further description would be necessary. However, the transmitter contains an audio frequency generator, which pulses at a given grid bias voltage, and for the signal modulation of the transmitter a conduit 34 is therefore provided from the code transmitter to the proper transmitter for alternatively connecting and disconnecting the required grid bias voltage from the audio frequency generator, so that a modulation will take place in the transmitter with a code of Morse signs or the like, determined by the code transmitter.

The code transmitter 22 thus has three different func-' tions to fulfill: It should control the phase reversal by means of the conduit 23 and the relay 24, it should further control the switching for higher or smaller course width, respectively, by means of the conduit 30 and the relay 29, and it should finally control the order of the codes in the transmitter by means of the conduit 34. There are difierent ways of constructing a code transmitter, which is capable of executing these three functions, and while such an arrangement is described below, consisting in three motor-driven contact discs, this is only to be regarded as one chosen arrangement for the purpose, which is especially suitable in cheaper and more simple systems, but the invention is not limited tothis arrangement. 1 a v iThe threefcontact discsare indicated 35, 86andx37. iltfis assumed that' they are drivenaround byzm'eans. of..a motor-a38 with such zassspeedthat a fiullturn'is described for i nstance in -tworrninntes. :Eaehofsthe contact :discs is .inaconne'ctiontwith the grounded pole or a source of voltin'their'eircumlierencesxconduoting segments-are introduced, which areishownin'rblack :in the drawing, Whereasthe segments indicaztedibywhiteiare assumed to be insulating. It issassumed thatihe contact discs rotate inithe directionznhthe arrows 743, when the system is Under these IPICWlSiOIlS' theiolloiving ways .themartiof' the contactudisc :35, at the arrow point 143., rsaid xpart of the :contactrdisc zbeing insulating, gets' under the bnnsh d0, gthenzthe=:connectionof zthe voltagetostherelay 29 iis cutnfi saidwrelayhaving been enertgizedduring half autum-ofi the :contact di-scs,:but;now being .deeenergized. The inductancev coil 527 istherebysconnected into-the circuitsof the -antenna 1d,..anddhis antenna will consequently radiate ,vvith decreased intensity, :which .causes in :the above vindicated smanner an -incerase of the; sharpness .=o.f course :dndication and a .decrease of the course angle, respectively. Simultaneously the earlier connectcd'tcondenser 32 isvswitched-wout, and the system functions withhigh shanpnes's :for' transmitting the signal, intended torgniding :the-vesselssinto the narrow Bay, but it :has .a :ran-ge :which is decreased .tto "a corresponding degree... a

At the same moment the circuit through the conduit 23-:to the relay 24 is opened as the brush 41 is on .a segment 50f: the insulating material onthe :contact .ring .36. During-:thisitime, -hoWever,::the-,:contact 'brush 42 will con tact the conductive segment on the circumference of the contact ring .37 Zthreeatimes,-and threemodulation @pulses will ube transferred =to. thetransmitter, so that the signal transmitted will correspondto-thedVlorse .code of the letter O, which is three moderately long dashes. During the opennintervlalubefor'e ithe. followingtequally long contact piece on the circumference :of the contact ring 37, the brush 41..will, however, contact the conductive segmerit onfthe-contact'ring36,"and'by means of the 'conduit 23 ffeed. current'to the relay "24, "which "causes a phase reversalcfthe signal'-frorn-the"antenna"-11. During-the time, when the phase direction of the signal from the antenna 11 is in this way reversed, only one pulse is trans mitted from the contact disc 37. It is therefore evident that when this procedure is repeated during the upper half turn of the contact discs as shown in the drawing, the signal containing three dashes (the letter will be heard stronger on one side of the correct course into the Bay, whereas the signal, containing one dash (the letter T) will be heard stronger on the other side of the correct course. This change of signals takes place with a high degree of sharpness, and consequently one will on board the vessel, which is exactly in the course direction, con tinuously hear equally long and equally strong signals, repeated at equal intervals. If the vessel should, however, get out of course, then either each fourth pulse will be heard stronger than the remaining pulses or Weaker than the remaining pulses, and the helmsman will then know, in which direction he has to turn in order to position the vessel on the correct course.

One minute or, in other words, the time of half a turn of the contact discs having run in this way, the contact brush 40 will contact the conductive segment on the contact disc 35. The relay 29 is thereby energized, and it will remain energized during the next half turn of the contact discs, which with the assumed speed of rotation will correspond to one minute. By means of the relay contact 28, the inductance coil 27 is then bypassed, and and the signal intensity from the antenna is consequently increased. Simultaneously the condenser 32 is ithe system will :liunction in again connected into: the circuittor restoring: the timingl now destroyed; After the lapseof: five scconds,1corre.- spending to 15 on the periphery ofthe contact disc, contact-brush 41 will contact a; conductive segmenton the contact ring '36, andlcnrrent is now closed through the conduetorizfa to the relay '24, which is attracted provide a switching off'of the. phase.- re erser of. them.- .tenna :10. Immediatelythereaiter theucontactv is closed between the contact disc 37 and the brush 42,:three1times at short intervals, .s'opthatthe code sign for-the! Morse letter S (three dots) is transfeiredrothe transmitter and transmitted through both of the antenna systems. Thereafter the contacting at. the; contact. 'discfifi leases, and the relay :24. returns? to its position .of rest, the; phase direction consequently being reversed on the current, fed to the antenna 10, and thereafter, by means of the contact disc 37 and thecontactbrush42, the Morse sign for N (one long and oneshort pulse) istransmitted. This procedure is thereafter continued during the remainderof of the turn of thecontact discs, until the initial points again contactthe contact brushes, all of the above de scribed procedure being thereaftcr repeated;

' i It =Wil-l,-however, be evident from-the above that during the secondminute, corresponding to the half circular periphery part of the discs, turned downwards in the figure, the Morse codes 8 and N will alternatively be transmitted, at the sametime as the-antenna '11 is reversed each time, so that one of the Morse codes will be heard stronger on one side of'the -course,-whereas she-other Morse code will-be heard stronger on the other sideof the course. Choosing nowthe phase pos'itionsof -the antenna 11 correctly it- Will benoted that-"the Morse code N "will beheard stronger on-avessel, which is accidentally deviating northwards from the course, whereas the-Morse codes will be heard stronger -on board a vessel, which is deviating southwards from the'course; "Dur'ingal-l er this-part of the function 'of, the "beacon the antenna '11 is, however, fed with-strong currenb-the-range is wide, so that the signals may be received far awayin open Water, and the sharpness of course indication-is not-ur'b necessarily great. The beacon will, in other words, -in periods, which may for instance last-each one minute, alternatively transmit according 'to a-first system andaccording to 'a second system. -*Dnring the-transmission according' to the first 'system-the beacon has-high sharpness of course indication and small range. The highsharpness of course indication requires, in order to be used completely, a transmission according to the complementary code principle. This principle does not necessarily mean that the two codes complementing each other should fill out the time fully, so that a continuous tone is obtained, but they may also be regarded as complementing each other, if one obtained a regularly repeated code of constant signal intensity, as will be the case, when the Morse codes of the letters 0 and T are combined into a continuously repeated series of equally long dashes, interrupted by equal intervals. During the transmission according to the other system, the beacon has high range but less sharpness of course indication, but it can be used across a rather wide approaching angle. Here the code is different, so that confusion will not result. This code giving can of course also be made in such a way that it is a complementary code, but this is not at all necessary. The complementary code is of importance only in such cases when one requires a high sharpness of course indication, but this is not the case, when transmitting according to the second system. The codes of the letters N and S also differ essentially from the codes of the letters 0 and T, and confusion may scarcely be assumed to appear, but they do not form mutually complementary codes.

The codes of the transmission according to the second system may suitably be chosen in such a way that they form simultaneously the identification signal of the directed radio beacon.

When navigating according to the above description,

it is, however, not at all suitable that the navigator exclusively listens to the transmission of one system, when he is far away at sea, or according to the other system, respectively, as soon as he can hear the signals reliably. On the contrary, cases may appear, when it is of great importance for the security of navigation that the navigator listen to both of the transmissions.

For instance cases may appear, when one has chosen the signal intensity of the antenna 11 during the transmission with high sharpness of course indication in such a way that the above mentioned angle, indicated by a is equal to 4. The tangent value of 4 is about 0.07, and the relation between the signal intensity during one code and during the other code will therefore in this case be for ot=1.

This equation will also be satisfied for a value of a=about 16". Assuming now that a vessel is approaching the mouth of the Bay with a course error of 16, then one can on board said vessel, by exclusively listening to the transmission with high sharpness of course indication, can be brought to the miscomprehension that the vessel is only 1 out of course, and one may then steer into dangerous waters with a catastrophe as a consequence. However, if one listens to the transmission with high sharpness of indication then this miscomprehension may be avoided. The risk of such mistakes has prevented in older systems increasing the sharpness of course indication. In a system according to the invention, however, by using both systems of transmission this disadvantage is overcome.

The invention is of course not limited to the form of execution thereof, described above and shown in the drawings, but different modifications of the invention may be made within its frame. It is for instance not necessary that the antenna 11, which has the sharp signal intensity in the direction of the course, the so-called course antenna, should also be switched between higher and lower signal intensity, but in certain cases, dependent upon the geographical and/ or nautical circumstances it may be desirable instead to switch the other one or the cross course antenna between a higher and a lower signal intensity.

What is claimed is: 1

1. A directed radio beacon comprising, in combination, a transmitter, a pair of frame antennas, means connecting said transmitter to said antennas whereby said antennas transmit a predetermined code, one of said antennas having a strong field intensity in a selected direction, the other of said antennas having a strong field intensity in a direction perpendicular to the selected direction, means including a filter device for periodically switching the transmission of one of said antennas between high and low signal intensities.

2. A radio beacon according to claim 1 and further including means for periodically reversing the phase of the transmission of one of said antennas.

3. A radio beacon according to claim 1 and further including a code transmitter connected to said transmitter for determining the code to be transmitted.

-4. A radio beacon comprising, a pair of frame antennas, an oscillator connected to said antennas, a code transmitter connected to said oscillator for determining the code to be transmitted, one of said antennas having a strong field in one direction and the other of said antennas having a strong field in a direction angularly disposed thereto, means for periodically switching the transmission of one of said antennas between high and low signal intensities.

5. A radio beacon according to claim 4 and further including means for periodically reversing the phase of the transmission of one of said antennas, said transmission switching means, said phase reversing means, and said code transmitter being operable by a common drive means.

6. A radio beacon according to claim 4, said code transmitter including means or difierentiating the code between periods of high signal intensity and periods of low signal intensity.

7. A radio beacon according to claim 4, said lastnamed means including an inductance coil and means for bypassing the inductance coil.

References Cited in the file of this patent UNITED STATES PATENTS 2,094,333 Smith Sept. 28, 1937 2,184,267 Alexanderson Dec. 26, 1939 2,272,611 Lair Feb. 10, 1942 

